Btrfs: introduce convert_extent_bit
If I have a range where I know a certain bit is and I want to set it to another
bit the only option I have is to call set and then clear bit, which will result
in 2 tree searches. This is inefficient, so introduce convert_extent_bit which
will go through and set the bit I want and clear the old bit I don't want.
Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 7d5e556..0ada0b7 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -894,6 +894,194 @@
goto again;
}
+/**
+ * convert_extent - convert all bits in a given range from one bit to another
+ * @tree: the io tree to search
+ * @start: the start offset in bytes
+ * @end: the end offset in bytes (inclusive)
+ * @bits: the bits to set in this range
+ * @clear_bits: the bits to clear in this range
+ * @mask: the allocation mask
+ *
+ * This will go through and set bits for the given range. If any states exist
+ * already in this range they are set with the given bit and cleared of the
+ * clear_bits. This is only meant to be used by things that are mergeable, ie
+ * converting from say DELALLOC to DIRTY. This is not meant to be used with
+ * boundary bits like LOCK.
+ */
+int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
+ int bits, int clear_bits, gfp_t mask)
+{
+ struct extent_state *state;
+ struct extent_state *prealloc = NULL;
+ struct rb_node *node;
+ int err = 0;
+ u64 last_start;
+ u64 last_end;
+
+again:
+ if (!prealloc && (mask & __GFP_WAIT)) {
+ prealloc = alloc_extent_state(mask);
+ if (!prealloc)
+ return -ENOMEM;
+ }
+
+ spin_lock(&tree->lock);
+ /*
+ * this search will find all the extents that end after
+ * our range starts.
+ */
+ node = tree_search(tree, start);
+ if (!node) {
+ prealloc = alloc_extent_state_atomic(prealloc);
+ if (!prealloc)
+ return -ENOMEM;
+ err = insert_state(tree, prealloc, start, end, &bits);
+ prealloc = NULL;
+ BUG_ON(err == -EEXIST);
+ goto out;
+ }
+ state = rb_entry(node, struct extent_state, rb_node);
+hit_next:
+ last_start = state->start;
+ last_end = state->end;
+
+ /*
+ * | ---- desired range ---- |
+ * | state |
+ *
+ * Just lock what we found and keep going
+ */
+ if (state->start == start && state->end <= end) {
+ struct rb_node *next_node;
+
+ set_state_bits(tree, state, &bits);
+ clear_state_bit(tree, state, &clear_bits, 0);
+
+ merge_state(tree, state);
+ if (last_end == (u64)-1)
+ goto out;
+
+ start = last_end + 1;
+ next_node = rb_next(&state->rb_node);
+ if (next_node && start < end && prealloc && !need_resched()) {
+ state = rb_entry(next_node, struct extent_state,
+ rb_node);
+ if (state->start == start)
+ goto hit_next;
+ }
+ goto search_again;
+ }
+
+ /*
+ * | ---- desired range ---- |
+ * | state |
+ * or
+ * | ------------- state -------------- |
+ *
+ * We need to split the extent we found, and may flip bits on
+ * second half.
+ *
+ * If the extent we found extends past our
+ * range, we just split and search again. It'll get split
+ * again the next time though.
+ *
+ * If the extent we found is inside our range, we set the
+ * desired bit on it.
+ */
+ if (state->start < start) {
+ prealloc = alloc_extent_state_atomic(prealloc);
+ if (!prealloc)
+ return -ENOMEM;
+ err = split_state(tree, state, prealloc, start);
+ BUG_ON(err == -EEXIST);
+ prealloc = NULL;
+ if (err)
+ goto out;
+ if (state->end <= end) {
+ set_state_bits(tree, state, &bits);
+ clear_state_bit(tree, state, &clear_bits, 0);
+ merge_state(tree, state);
+ if (last_end == (u64)-1)
+ goto out;
+ start = last_end + 1;
+ }
+ goto search_again;
+ }
+ /*
+ * | ---- desired range ---- |
+ * | state | or | state |
+ *
+ * There's a hole, we need to insert something in it and
+ * ignore the extent we found.
+ */
+ if (state->start > start) {
+ u64 this_end;
+ if (end < last_start)
+ this_end = end;
+ else
+ this_end = last_start - 1;
+
+ prealloc = alloc_extent_state_atomic(prealloc);
+ if (!prealloc)
+ return -ENOMEM;
+
+ /*
+ * Avoid to free 'prealloc' if it can be merged with
+ * the later extent.
+ */
+ err = insert_state(tree, prealloc, start, this_end,
+ &bits);
+ BUG_ON(err == -EEXIST);
+ if (err) {
+ free_extent_state(prealloc);
+ prealloc = NULL;
+ goto out;
+ }
+ prealloc = NULL;
+ start = this_end + 1;
+ goto search_again;
+ }
+ /*
+ * | ---- desired range ---- |
+ * | state |
+ * We need to split the extent, and set the bit
+ * on the first half
+ */
+ if (state->start <= end && state->end > end) {
+ prealloc = alloc_extent_state_atomic(prealloc);
+ if (!prealloc)
+ return -ENOMEM;
+
+ err = split_state(tree, state, prealloc, end + 1);
+ BUG_ON(err == -EEXIST);
+
+ set_state_bits(tree, prealloc, &bits);
+ clear_state_bit(tree, prealloc, &clear_bits, 0);
+
+ merge_state(tree, prealloc);
+ prealloc = NULL;
+ goto out;
+ }
+
+ goto search_again;
+
+out:
+ spin_unlock(&tree->lock);
+ if (prealloc)
+ free_extent_state(prealloc);
+
+ return err;
+
+search_again:
+ if (start > end)
+ goto out;
+ spin_unlock(&tree->lock);
+ if (mask & __GFP_WAIT)
+ cond_resched();
+ goto again;
+}
+
/* wrappers around set/clear extent bit */
int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
gfp_t mask)
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 7b2f0c3..cea445d 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -214,6 +214,8 @@
gfp_t mask);
int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
gfp_t mask);
+int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
+ int bits, int clear_bits, gfp_t mask);
int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
struct extent_state **cached_state, gfp_t mask);
int find_first_extent_bit(struct extent_io_tree *tree, u64 start,